The modulator comprises two silicon phase-shifters that are integrated in a nested Mach-Zehnder configuration. The company optimized electrode arrangements and doping profiles in the phase-shifters, which materializes high-speed performance of >40 Gbps DQPSK and >60Gbps QPSK modulation at less than 10dB fiber-to-fiber loss. Moreover, dispersion tolerance of more than +/-80 ps/nm is recorded at the 44.6 Gbps DQPSK transmission.